Recently, buildings have become more airtight to inhibit a desired temperature within a building to change toward an undesired temperature; either hotter or colder. When a heating system is used in a cold climate for a building that has significant air exchange with the outside, airflow can cause the inside of the building to decrease in temperature as colder air penetrates into the building and warmer air escapes. On the other hand, when a cooling system is used to cool the inside of a building in a warmer climate that has significant air exchange with the outside, airflow can cause the inside of the building to increase in temperature as warmer air penetrates into the building and cooler air escapes. The improvements in airtight buildings have sought to overcome the problems of inefficient indoor temperature control due to significant air exchange from inside to outside of the building. The airtightness has been increased from the perspective of saving energy and, possibly to prevent global warming due to less resources being used for energy.
While the use of building materials with high thermal insulation properties enables control of thermal movement between the inside and outside of a building, it also makes release of warmed air from the inside more difficult. The buildup of heat and increased temperatures inside a building can necessitate active ventilation of the building using fans to exchange the warmer indoor temperature to the cooler outdoor temperature. While using fans may be effective in exchanging indoor and outside air, they consume energy and may not provide sufficient thermal movement without a large vent or opening that itself can be problematic for indoor temperature control. Air conditioning with cooling systems can decrease temperatures, but they consume a lot of energy and can cause undesirable condensation.